Genome-wide RNAi selection identifies a regulator of transmission stage-enriched gene families and cell-type differentiation in Trypanosoma brucei

• Published in: PLoS pathogens Vol. 13; no. 3; p. e1006279
• Main Authors: Rico, Eva, Ivens, Alasdair, Glover, Lucy, Horn, David, Matthews, Keith R
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23.03.2017; Public Library of Science (PLoS)
• Subjects: Animals; Biology; Biology and life sciences; Cell cycle; Cell Differentiation; Cell Differentiation - genetics; Cell fate; Differentiation (biology); Disease Models, Animal; Disease transmission; Enrichment; Evolution; Female; Flies; Flow Cytometry; Gene expression; Gene Expression Regulation; Gene Expression Regulation - genetics; Gene families; Genetic aspects; Genome-Wide Association Study; Genomes; Immunoblotting; Immunology; Infections; Life Sciences; Mammals; Medicine and Health Sciences; Messenger RNA; Mice; Midgut; Parasites; Proteins; Protozoa; Protozoan Proteins; Protozoan Proteins - biosynthesis; Protozoan Proteins - genetics; Repressors; RNA Interference; RNA-Binding Proteins; RNA-Binding Proteins - biosynthesis; RNA-Binding Proteins - genetics; RNA-mediated interference; Transcription; Transfection; Tropism; Trypanosoma brucei; Trypanosoma brucei brucei; Trypanosoma congolense; Trypanosoma vivax; Trypanosome; Trypanosomiasis, African; Trypanosomiasis, African - genetics; Trypanosomiasis, African - transmission; Scotland; Edinburgh Scotland
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1006279

Trypanosoma brucei, causing African sleeping-sickness, exploits quorum-sensing (QS) to generate the 'stumpy forms' necessary for the parasite's transmission to tsetse-flies. These quiescent cells are generated by differentiation in the bloodstream from proliferative slender forms. Using genome-wide RNAi selection we screened for repressors of transmission stage-enriched mRNAs in slender forms, using the stumpy-elevated ESAG9 transcript as a model. This identified REG9.1, whose RNAi-silencing alleviated ESAG9 repression in slender forms and tsetse-midgut procyclic forms. Interestingly, trypanosome surface protein Family 5 and Family 7 mRNAs were also elevated, which, like ESAG9, are T. brucei specific and stumpy-enriched. We suggest these contribute to the distinct transmission biology and vector tropism of T. brucei from other African trypanosome species. As well as surface family regulation, REG9.1-depletion generated QS-independent development to stumpy forms in vivo, whereas REG9.1 overexpression in bloodstream forms potentiated spontaneous differentiation to procyclic forms in the absence of an external signal. Combined, this identifies REG9.1 as a regulator of developmental cell fate, controlling the expression of Trypanosoma brucei-specific molecules elevated during transmission.